1. Field of the Invention
The present invention relates to a process for producing a semiconductor having a thin film of a fluorine resin as a protective film.
2. Discussion of Background
Heretofore, it has been usually difficult to form a thin film of a fluorine resin by coating, since the fluorine resin is usually insoluble in a solvent. However, fluorine resins soluble in special solvents have been developed as disclosed in Japanese Unexamined Patent Publications No. 238111/1988 and No. 260932/1988 and U.S. Pat. No. 4,754,009, and their application to semiconductor protective films utilizing their electrical properties and low water absorptivity, has been disclosed in European Patent 0393682.
On the other hand, an organic thin film used as a protective film of a semiconductor is required to be subjected to fine processing such as local perforation processing to take electrical connection or wire bonding, and photolithography using a photoresist is usually employed for this purpose.
However, the above fluorine resins have a high fluorine content and an extremely low surface energy, and therefore they tend to repel a photoresist solution, whereby it has been difficult to uniformly coat it by e.g. spin coating, and it has been difficult to apply fine processing by photolithography.
Further, in order to improve the uniformity in the application of a photoresist, it has been common to employ a method wherein an adhesion-improving agent such as HMDS (hexamethyl disilazane) is coated in a liquid state, and a photoresist is coated thereon, followed by photolithography. However, the above-mentioned fluorine resins tend to repel even such a solution, and it has been difficult to improve the adhesion by coating. Thus, there has been a problem that it is required to heat the adhesion-improving agent to conduct treatment by its vapor, or it is required to improve the wettability of the surface by such a method as vapor deposition of e.g. a metal.